Community antenna television (CATV) systems and many broadband data transmission systems rely on a network of coaxial cables to carry a wide range of radio frequency (RF) transmissions with low amounts of loss and distortion. A covering of plastic or rubber adequately seals an uncut length of coaxial cable from environmental elements such as water, salt, oil, dirt, etc. However, the cable must attach to other cables, components and/or to equipment (e.g., taps, filters, splitters and terminators) generally having threaded ports (hereinafter, “ports”) for distributing or otherwise utilizing the signals carried by the coaxial cable. A service technician or other operator must frequently cut and prepare the end of a length of coaxial cable, attach the cable to a coaxial cable connector, or a connector incorporated in a coaxial cable system component, and install the connector on a threaded port. This is typically done in the field. Environmentally exposed (usually threaded) parts of the components and ports are susceptible to corrosion and contamination from environmental elements and other sources, as the connections are typically located outdoors, at taps on telephone polls, on customer premises, or in underground vaults. These environmental elements eventually corrode the electrical connections located in the connector and between the connector and mating components. The resulting corrosion reduces the efficiency of the affected connection, which reduces the signal quality of the RF transmission through the connector. Corrosion in the immediate vicinity of the connector-port connection is often the source of service attention, resulting in high maintenance costs.
Numerous methods and devices have been used to improve the moisture and corrosion resistance of connectors and connections. These include, for example, wrapping the connector with electrical tape, enclosing the connector within a flexible boot which is slid over the connector from the cable, applying a shrink wrapping to the connector, coating the connector with plastic or rubber cement, and employing tubular grommets of the type discussed in U.S. Pat. No. 4,674,818 (McMills, et al.) and in U.S. Pat. No. 4,869,679 (Szegda), for example.
Although these methods work, more or less, if properly executed, they all require a particular combination of skill, patience, and attention to detail on the part of the technician or operator. For instance, it may be difficult to apply electrical tape to an assembled connection when the connection is located in a small, enclosed area. Shrink wrapping may be an improvement under certain conditions, but shrink wrap application typically requires applied heat or chemicals, which may be unavailable or dangerous. Rubber-based cements eliminate the need for heat, but the connection must be clean and the cement applied somewhat uniformly. These otherwise attainable conditions may be complicated by cold temperatures, confined or dirty locations, etc. Operators may require additional training and vigilance to seal coaxial cable connections using rubber grommets or seals. An operator must first choose the appropriate seal for the application and then remember to place the seal onto one of the connective members prior to assembling the connection. Certain rubber seal designs seal only through radial compression. These seals must be tight enough to collapse onto or around the mating parts. Because there may be several diameters over which the seal must extend, the seal is likely to be very tight on at least one of the diameters. High friction caused by the tight seal may lead an operator to believe that the assembled connection is completely tightened when it actually remains loose. A loose connection may not efficiently transfer a quality RF signal causing problems similar to corrosion.
Other seal designs require axial compression generated between the connector nut and an opposing surface of the port. An appropriate length seal that sufficiently spans the distance between the nut and the opposing surface, without being too long, must be selected. If the seal is too long, the seal may prevent complete assembly of the connector or component. If the seal is too short, moisture freely passes. The selection is made more complicated because port lengths may vary among different manufacturers.
Moreover, even connectors that incorporate well-designed seals can be prone to problems. For example, it is very difficult to ensure that all connectors, especially those installed in the field, are sufficiently tight as installed. Plus, those that are tightly installed still can loosen over time. This is unfortunate, since if a connection/connector is or becomes loose, even slightly, the conductive path through the connector can be lost/disrupted, thus causing various negative system performance issues to arise. For example, loosened cable connections are prone to suffering from radio frequency interference (RFI) conditions, such as RFI ingress (i.e., when the loosened cable acts as an antenna and picks up interfering radio waves from HAM radio transmitters and broadcast radio stations) and/or RFI egress (i.e., when the loosened cable emits signals that disturb wireless services such as HAM radio transmitters). Although there are various techniques for mitigating RFI interference (e.g., cancellation based on the common-mode signal), it would be preferable to solve the problem at hand, namely the loss/disruption of a conductive path due to loosening of one or more connections within the connector, as opposed to treating the symptoms of the problem.
In view of the aforementioned shortcomings and others known by those skilled in the art, there is a need for a seal and a sealing connector that addresses these shortcomings and provides other advantages and efficiencies.